| A weakly nonlinear baroclinic geostrophic adjustment in a rotating basin is investigated in a laboratory study. The adjustment process is separable into a linear phase followed by a nonlinear phase on the basis of scaling arguments. This work describes in detail the hydrodynamics and energetics of the linear phase of the adjustment process from an initial step height discontinuity in the density interface ΔH to a final response consisting of geostrophic and periodic components. For a forcing length scale r f equal to the basin radius R 0 , the geostrophic component consists of a double gyre while the periodic component is composed of baroclinic Kelvin and Poincaré waves. The Burger number S = R i /r f (R i = the baroclinic Rossby radius of deformation) and the scaled depth ε = ΔH/H 1 (H 1 = the upper layer depth) characterise the response of the adjustment process.In particular, an excellent agreement between an analytical solution and the laboratory measurements is observed for times τ < ½ ε -1 , indicating this is the duration of the linear phase of the adjustment process. Over this timescale, the analytical solution can thus be used to calculate the energetics of the baroclinic geostrophic adjustment in a rotating basin. The results of this energetics study are found to compare favourably with previous studies with partitioning of energy between the geostrophic and periodic components exhibiting a strong dependence on S. |
|
|